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Introduction

  1. Pharmacology. Esmolol is a short-acting cardioselective beta-adrenergic blocker with no intrinsic sympathomimetic or membrane-depressant activity. In usual therapeutic doses, it causes little or no bronchospasm in patients with asthma. Esmolol produces peak effects within 6-10 minutes of administration of an intravenous bolus. It is hydrolyzed rapidly by red blood cell esterases, with an elimination half-life of 9 minutes; therapeutic and adverse effects disappear within 30 minutes after the infusion is discontinued.
  2. Indications
    1. Rapid control of supraventricular and ventricular tachyarrhythmias and hypertension, especially if caused by excessive sympathomimetic activity (eg, stimulant drugs, hyperthyroid state).
    2. Reversal of hypotension and tachycardia caused by excessive beta-adrenergic activity resulting from theophylline or caffeine overdose.
    3. Control of ventricular tachyarrhythmias caused by excessive myocardial catecholamine sensitivity (eg, chloral hydrate and chlorinated hydrocarbon solvents).
  3. Contraindications
    1. Contraindications include hypotension, bradycardia, and congestive heart failure secondary to intrinsic cardiac disease or cardiac-depressant effects of drugs and toxins (eg, cyclic antidepressants, barbiturates, calcium channel antagonists).
    2. Hypertension caused by alpha-adrenergic or generalized stimulant drugs (eg, cocaine, amphetamines), unless esmolol is coadministered with a vasodilator (eg, nitroprusside or phentolamine). Paradoxical hypertension may result from an unopposed alpha effect, although it is less likely than that associated with the use of a nonspecific beta-adrenergic blocker (propranolol).
  4. Adverse effects
    1. Hypotension, bradycardia, and cardiac arrest may occur, especially in patients with intrinsic cardiac disease or cardiac-depressant drug overdose.
    2. Bronchospasm may occur in patients with asthma or chronic bronchospasm, but it is less likely than with propranolol or other nonselective beta-blockers and is rapidly reversible after the infusion is discontinued.
    3. Esmolol may mask physiologic responses to hypoglycemia (tremor, tachycardia, and glycogenolysis) and, therefore, should be used with caution in patients with diabetes.
    4. Avoid extravasation. Infusion site reactions include irritation as well as necrosis and thrombophlebitis.
    5. Use in pregnancy. FDA Category C (indeterminate). This does not preclude its short-term use for a seriously symptomatic patient (Introduction). High-dose infusion may contribute to placental ischemia.
  5. Drug or laboratory interactions
    1. Esmolol may transiently increase the serum digoxin level by 10-20%, but the clinical significance of this is unknown.
    2. Esmolol may increase the risk of hypotension, bradycardia, AV conduction impairment if used concurrently with calcium channel antagonists, sympatholytics (clonidine), or amiodarone.
    3. Recovery from succinylcholine-induced neuromuscular blockade may be delayed slightly (5-10 minutes). Similarly, esmolol metabolism may be inhibited by anticholinesterase agents (eg, organophosphates).
    4. Esmolol is not compatible with sodium bicarbonate solutions.
  6. Dosage and method of administration
    1. Dilute before intravenous injection to a final concentration of 10 mg/mL with 5% dextrose, lactated Ringer injection, or saline solutions.
    2. Give as an intravenous infusion, starting at 0.025-0.05 mg/kg/min and increasing as needed up to 0.2 mg/kg/min (average dose, 0.1 mg/kg/min). Steady-state concentrations are reached approximately 30 minutes after each infusion adjustment. A loading dose of 0.5-1.0 mg/kg should be given over 30 seconds to 1 minute if more rapid onset of clinical effects (5-10 minutes) is desired.
    3. Infusion rates greater than 0.2 mg/kg/min are likely to produce excessive hypotension. At rates greater than 0.3 mg/kg/min, the beta-blocking effects lose their beta1 selectivity.